The invention is based on an electromagnetic actuator according to the preamble of claim 1.
Known electromagnetic actuators for activating a valve usually include an electromagnet which acts on a correspondingly designed armature surface of a moveable armature by way of at least one pole face in an effective range using a magnetic field generated by a coil. When the actuator is activated, the armature is drawn out of a starting position with the armature surface in the direction of the pole face, and the valve is opened or closed directly by the armature or indirectly by way of an armature plunger, and, in fact, usually against spring resistance. In an end position, the armature surface lies on the pole face.
In order to enable the electromagnet to act on the armature along a long stroke and, as a result, to make a long travel distance possible, it is known to design the pole face and the corresponding armature surface to be conical and/or stepped. Using high steps or a steep taper, a short, direct path between the pole face and the armature surface can be achieved despite a long travel distance in the starting position and from the start of the correcting movement onward and, as a result, a relatively strong force on the armature can be achieved from the beginning onward. Compared to a pole face which is situated basically perpendicular to the travel distance, however, a smaller force is achieved immediately before and in the final position.
The invention is based on an electromagnetic actuator, especially for activating a valve, having at least one electromagnet that acts on a correspondingly designed armature surface of a moveable armature by way of at least one first conical and/or stepped pole face in a first effective range using a magnetic field generated by at least one coil.
It is proposed that the electromagnet act on a corresponding armature surface by way of at least a second pole face in at least a second effective range. A long travel distance having a relatively strong force from the start of the travel distance onward can be achieved advantageously with the first effective range using a first pole face having a steep taper or high steps. Additionally, a strong force can be achieved in the final position with the second effective range, especially using a second pole face situated basically perpendicular to the direction of movement.
Especially advantageously, the conical and/or stepped first pole face is situated at least partially within the coil, advantageously completely inside the coil. The radial and axial space inside the coil can be used advantageously and additional space can be saved.
Furthermore, space can be saved by situating the second pole face in the direction of movement of the armature between the armature and the coil. In order to achieve the greatest possible force in the end position using the second pole face, it is advantageously designed basically perpendicular to the direction of movement of the armature and thereby requires only small axial space. An especially large part of the cross-sectional area of the coil can be used as pole face and a small actuator with strong force can be achieved. Moreover, it is possible to arrange the first, second or a third pole face radially outside the coil that acts on a corresponding armature surface.
The radial inner region of the second pole face can be used advantageously to safely guide the armature in the direction of movement in two places separated by a large distance.
In a design of the invention it is proposed that a component forming the second pole face be designed as a single piece with a guide of the armature. A favorable magnetic flux can be achieved and additional components, space, and assembly expenditure can be saved. Moreover, an especially large second pole face can be achieved on small space. The guide can also be formed out of an additional component having special sliding properties, however.
The solution according to the invention can be used in various electromagnetic actuators that appear appropriate to the expert, especially advantageously however in electromagnetic actuators for activating a valve that require a long travel distance on small space and the greatest possible force in the end position, for example in a solenoid valve for a water circuit, etc.